The background of this invention is problems and disadvantages associated with the prior art concerning introduction of a treatment fluid, for example a remedial seal, into an annulus in a well after completion of the well and during the operating phase thereof. It is emphasized, however, that the present invention may be used in any phase during the lifetime of a well.
With respect to remedial seals, and according to prior art, it is customary to use various well packers to isolate zones, for example one or more reservoir zones, along a well pipe when placed in, or being placed in, a well. Packers of this type are normally placed on the outside of the specific well pipe and before it is conveyed into the well. This type of packer is commonly referred to as an external casing packer—“ECP”, for example a so-called inflatable packer. When the well pipe has been conveyed and is positioned at the corrected location in the well, the packer(s) is/are activated in the annulus around the well pipe and is/are forced outwards and against surrounding rocks, or against a surrounding well pipe. Activation of such a packer may be carried out hydraulically and/or mechanically. A so-called swell packer may also be used that will expand upon contact with, for example, oil and/or water in the well. Packer setting techniques of this type constitute prior art.
Yet further, during the post-completion phase of a well, and particularly in connection with recovery of hydrocarbons from a reservoir, production-related problems or conditions may arise that require or generate a need for installing one or more additional annulus packers in the well. Installation of such remedial annulus packers may form part of an appropriate production management strategy, water injection management strategy or reservoir drainage strategy. Alternatively, such an installation may be carried out to remedy an acute situation in the well. Accordingly, a need may exist for isolating one or more zones in a well, for example in a production well or in an injection well, and the need may arise at any time throughout the lifetime of a well. Normally, the need will be the greatest in horizontal wells and highly deviated wells. Deficient or failing zone isolation may restrain or prevent various efforts to stimulate the recovery from a well, which may reduce the recovery factor and profitability of the well and/or the reservoir. Insufficient zone isolation may also lead to unfortunate and/or dangerous conditions in the well. It may also concern other isolation/treatment needs in any annulus in a well, including an annulus between an uncased borehole wall and a well pipe, or an annulus between two well pipes. Thus it may concern, for example, a cemented annulus requiring after-treatment, or an annulus between two well pipes, along the entire length or longitudinal sections of the well.
The following examples point out some well conditions in which effective and selective annulus sealing may be of great significance to the performance of a well:                Blocking of undesirable fluid flows, for example a water flow, from specific zones/intervals and into a production well, such as undesirable fluid flows from faults, fractures and highly permeable regions of surrounding rocks;        Blocking of undesirable fluid flows to so-called “thief-zones” in an injection well, such as undesirable fluid flows to faults, fractures and highly permeable regions of surrounding rocks; and        Selective placement of well treatment chemicals, including scale inhibitors and stimulation chemicals, in individual zones of a production well or injection well.        